The invention relates to painting and in particular to the application of a paint to a substrate in such a way as to create a wood grain effect. The invention is especially useful in the application of a paint to an article having a plastic surface to which paint will not ordinarily bond; an example being a moulding, e.g. an extrusion, of unplasticised polyvinylchloride, more usually known as PVC(u). For convenience - but not by way of limitation - the invention will be described with particular reference to that use.

It is well known to use PVC(u) as a material for making a variety of products useful in the building and allied industries; window frames, cladding and the like are examples which come readily to mind. These articles are typically white because ordinary paint cannot readily be applied to the formed articles and/or will weaken the physical properties thereof. While it is possible to add a colouring agent to the mix of which the article is extruded, that adds to the cost and provides a uniform colour, not the regions of contrasting colour which is typical of a wood grain effect.

It is known to use a paint comprising quick drying formulation of a carrier containing a colouring agent and which penetrates and

bonds to plastic.

It is one object of the invention to provide a method for applying a paint to a substrate to produce a wood grain effect.

In one aspect the invention provides a method of making a wood grain colour effect on a surface of a substrate, the method comprising the step of placing a stencil over the surface, the stencil comprising at least two elongate elements, the elements being flexibly mounted within the stencil, and applying a paint to the area of the surface exposed between the elements thereby to provide an elongate painted area the opposite sides of which are defined by the edge shape of the adjacent elements.

Preferably the stencil comprises a plurality of the elements flexibly connected together by flexible strap members. In a preferred feature the stencil is applied to the substrate under tension applied to the flexible strap members.

Preferably the elements are of varying cross-sectional area along their length, and are each of different shape.

Because plastics profiles are made long the stencil preferably comprises lengths which are j oined together in end-to-end relation.

In a much preferred feature a coating of one paint is pre- applied to the substrate before the stencil is placed thereon. The two paints may be different or the first and second paint coatings may be the same colour but applied to different densities.

Most preferably the paint is a dye or pigment in a carrier and which is selected to penetrate and bond to the substrate. Preferably the paint is a quick drying formulation and may be applied as an aerosol or using spray equipment.

The invention is especially useful where the substrate is any one or more of a plastics such as polyvinylchloride (unplasticised or plasticised) ; aerylonitrite-butadiene styrene; Nylon; polycarbonate; ethylene propylene diene monomer; polyurethane; glass or fibre reinforced plastics; or the like. Other substrates include brick, blocks, concrete, fibre substrates, e.g. paper, cardboard, etc.

The wood grain effect obtained in the invention may be intended to simulate the natural grain, i.e. general direction or arrangement of fibres obtained with natural woods. The grain which tends to follow the natural figuration due to growth rings is usually composed of different grains, e.g. straight, irregular, sloping, wavy, side, end or the like. The grain may however be an artificial one and may include purpose designed

patterns .

The wood grain effect may be chosen from a variety of natural woods or simulated natural woods, examples being oak, ash, beech, elm, mahogany, pine, rosewood, sapele, teak, walnut or the like.

In another aspect the invention provides a stencil for use in a method as defined, the stencil comprising at least two spaced apart elongate elements, the elements being flexibly mounted within the stencil.

Preferably the elongate elements are joined together by flexible strap members; the elongate elements are of varying cross- sectional shape along their length; and the elements are each of different shape. The stencil may be mounted in a support frame.

In another aspect, the invention provides an extruded profile of a plastics material, the profile being of a shape appropriate to a product for use in building, at least one surface of the profile being painted, the paint presenting a wood grain effect. Preferably the profile is shaped to define a wall of the frame of a window, door or the like; a panel for use in cladding or the like.

In order that the invention may be well understood it will now be described by way of example with the reference to the

accompanying diagrammatic drawings, in which:

Figure 1 is a plan view of a plastics profile at three stages of treatment by a method of the invention;

Figure 2 is a perspective view of the stencil used in the method;

Figure 3 is an end view showing the stencil on a representative profile; and

Figure 4 is an elevation of a stencil of the invention in use on vertical side wall of an installed window frame.

As shown diagrammatically in Figure 1, in the overall method of the invention at stage A, a first coating of a background colour Gl is uniformly applied to the surface of a substrate 1, a second coating is applied using the stencil S of the invention at stage B to form contrasting coloured areas G2 and a final coating is applied at stage C.

As shown best in Figure 2, the stencil S comprises a plurality of spaced apart rods 2 held together at their ends by flexible straps 3, so that the stencil is a flexible structure and can be rolled up in the manner of a rug. The straps 3 are held to the rods 2 at the ends thereof by bolts or the like 4. The straps

may be of wire, rope or the like. The rods 2 are of non-uniform or varying cross-sectional area along their length and no two adjacent rods are alike, so that the space between adjacent rods varies in width and no two spaces are identical. The shape of the individual rods 2 is selected so that adjacent rods define a space in between which simulates the natural figuration due to growth rings typical of a particular wood, e.g. teak. Because the straps 3 are flexible, the degree of tension applied in use will determine the width of the spaces and the stencil may be wrapped around or form a cradle about the profile.

The substrate 1, typically a profile for a side wall or cross member of a window (and as exemplified in Figure 3) is an extrusion of PVC(u). In use the profile is moved on a conveyor from left to right, as seen in Figure 1. At station A a coating Gl of a background paint of spray is applied as say an aerosol from a gun 5. The background layer may be a relatively light colour. At stage B, the stencil S is laid on the profile, as shown in Figure 3, the rods falling randomly on to the painted surface according to the degree of tension applied to the straps 3 and the specific contours of the profile. A second paint coating is applied over and through the stencil S to provide contrasting areas G2 reproducing the intended wood grain effects. The fact that one colour G2 may overlap the background colour Gl is a better simulation of natural wood grain. The second paint may be a different colour to the first or the same colour applied

to a different density. At stage C a final coating, e.g. a lacquer or toner is applied for a finish.

In the embodiment of Figure 4, the stencil of the invention is applied to a side wall 10 comprising a plastics extrusion installed in a window. The stencil is mounted in a frame 11, which is fixed, e.g. clamped or bolted to the wall 10 and then coatings of paint are applied using a hand gun or aerosol can 12. Adjacent areas of the window are masked. In this way the wood grain effect may be applied as a subsequent treatment to an already installed profile. The same technique may be used on cladding, tiles, ceiling beams, and the like.

The invention is not limited to the embodiment shown. The elongate elements may comprise lengths joined together in flexible manner to cause graining of convex or concave surfaces; the lengths may be joined for this purpose using say tensioning wire. The third stage may be omitted; more than one stencil may be present; the stencil may be applied to different surfaces. The substrate may be indexed or the spray gun indexed so that adjacent sides of the substrate may be sprayed at the one station. The substrate may be fixed and the guns 4 moved therealong.